1. Field of the Invention
The invention relates generally to the field of turbocharged engines. More specifically, the invention relates to control of the wastegate on a turbocharged engine. The invention is applicable to gasoline or diesel engines.
The wastegate is a valve which, when opened, allows exhaust gas from the engine to bypass the turbine inlet of the turbocharger. This “waste” of exhaust gas limits the turbine inlet pressure, which thereby limits the turbine speed, which further limits the intake manifold boost pressure generated by the turbocharger.
2. Description of the Related Art
There are many different wastegate controllers in the prior art, with a variety of mechanisms for adjusting or maintaining a limiting pressure at the turbine inlet.
U.S. Pat. No. 3,931,712 by Keller, Internal Combustion Engine Turbocharger Pressure Control Regulators discloses a differential pressure activated control system having non-mechanical, remotably controllable, biasing means.
U.S. Pat. No. 4,169,355 by Walsham et al., Turbocharger Wastegate Valve, discloses a cylindrical wastegate valve arrangement which claims decreased likelihood of seizing in the closed position over a conventional poppet valve wastegate.
U.S. Pat. No. 4,174,617 by Jalali-Karchay, Turbocharger Control System, discloses a method of comparing the magnitude of a sea-level reference parameter, with an electrical parameter in a pressure-temperature sensor or sensors coupled to the air induction system of an internal combustion engine, particularly a turbocharged engine. A control signal may be derived from this comparison which will automatically adjust the flow of exhaust gas to the turbocharger and will automatically result in constant engine power from sea level to a critical altitude.
U.S. Pat. No. 4,179,247 by Osborn, Turbocharger having Variable Area Turbine Nozzles, discloses a turbocharger with variable nozzle vane geometry. The vane geometry is varied by means of a control rod loaded with a spring and affixed to a diaphragm sensitive to the compressor output pressure.
U.S. Pat. No. 4,251,050 by McInerney discloses a Turbocharger Control Actuator. The control actuator for a turbocharger comprises a diaphragm-displaced actuator rod projecting outwardly from an actuator housing through a seal permitting axial and angular rod movement for variably positioning a turbocharger wastegate valve.
U.S. Pat. No. 4,256,019 by Braddick, Turbocharger Control Actuator, discloses a wastegate control rod actuating cylinder with a spring-loaded diaphragm and pneumatic coupling points for loading both sides of the diaphragm, such that the control rod is responsive to the differential pressure across the diaphragm.
U.S. Pat. No. 4,283,912 by Cholvin, Turbocharger Control, discloses a pneumatically-operated wastegate valve controller designed to be largely insensitive to altitude variation.
U.S. Pat. No. 4,377,070 by Shadbourne, Turbocharger Control Actuator, discloses a wastegate actuator responsive to compressor inlet pressure during part load engine operation and turbine inlet pressure during full load engine operation.
U.S. Pat. No. 4,403,538 by Rise, Turbocharger Control Actuator, discloses a wastegate control rod actuator comprising a cannister with a pressure sensitive diaphragm attached to the rod and a preloading spring. The rod seal in the cannister is designed to allow for motion of the rod other than strictly axial, and therefore supporting multiple valve types with complex linkages.
U.S. Pat. No. 4,476,682 by McInerney, Turbocharged Internal Combustion Engine having an Altitude Compensated Boost Control and Method for its Operation, discloses a pneumatically controlled altitude compensating boost control for maintaining a constant intake manifold pressure on a turbocharged engine having a wastegate valve for selectively bypassing engine exhaust gas around the turbine.
U.S. Pat. No. 4,490,622 by Osborn, Turbocharger and adaptations thereof, is a continuation-in-part of U.S. Pat. No. 4,179,247 cited above.
U.S. Pat. No. 4,630,445 by Parker, Wastegate Valve For Internal Combustion Engine Turbocharger, discloses a wastegate valve for an internal combustion engine turbocharger comprising a valve head carried by a valve stem and arranged to cooperate with a valve seat in a bypass passage, the valve stem being mounted in a valve guide for movement between a position in which the valve head and valve seat cooperate to close the valve and a position in which the valve head is spaced from the valve seat.
U.S. Pat. No. 4,655,043 by McInerney, Turbocharger, discloses a lightweight, compact turbocharger for small internal combustion engines having a reduced number of component parts for simplified construction, an improved bearing structure and a novel means of transmitting control pressure to the actuator. The control rod attached to the turbine inlet poppet valve actuator is preloaded by a spring housed in a cannister.
U.S. Pat. No. 5,146,753 by Potter, Turbocharged Internal Combustion Engine Having Reduced High Speed Emissions, discloses an internal combustion engine system having reduced high speed emissions comprising an exhaust driven supercharger having turbine pressure dependent control means for regulating turbine pressure and turbine speed to a substantially constant value to produce a decreasing compressor pressure profile with increasing engine speed and to reduce mass air flow through the engine during high speed operation, thereby reducing engine emissions and improving durability.
U.S. Pat. No. 5,172,552 by Elpern et al., Turbocharger With Flexible Cable Wastegate Operating Linkage, discloses an exhaust driven turbocharger includes a wastegate valve which is operated by a pneumatic actuator mounted on the outer edge of the compressor housing. A portion of the linkage interconnecting the actuator with the wastegate valve includes a flexible cable
U.S. Pat. No. 5,205,125 by Potter, Turbocharged Internal Combustion Engine Having Exhaust Gas Pressure Actuated Turbine Bypass Valve, is a divisional application from the parent application of U.S. Pat. No. 5,146,753 cited above.
U.S. Pat. No. 5,487,273 by Elpern et al., Turbocharger Having Pneumatic Actuator With Pilot Valve, discloses a pneumatic actuator for controlling the wastegate valve of an exhaust gas driven turbocharger includes a pilot piston which is responsive to boost pressure to open only when a desired boost pressure is attained. Accordingly, premature opening of the wastegate valve is avoided because the main actuator piston is maintained at atmospheric pressure until the desired actuating pressure is attained.
U.S. Pat. No. 5,701,741 by Halsall, Turbochargers For Internal Combustion Engines, discloses an electrically-driven wastegate actuator.
U.S. Pat. No. 6,405,535 by McEwan, Turbocharger with Wastegate Actuator discloses a pneumatic wastegate actuator with a rigid pneumatic line between the compressor housing and the wastegate actuator can.
There are large numbers of turbocharger wastegate controllers in use today. One example of an existing wastegate controller is the factory wastegate controller utilizing a spring-loaded canister, as used in 1993 to 1997 GM® turbo-diesel engines from General Motors Corporation, Wilmington Del. The preferred embodiment of the present invention is an after-market replacement for such a factory wastegate controller. As it is central to the description of the present invention, the prior art controller is described in some detail here. The use of this specific example does not establish the scope of the present invention. The invention is applicable to both gasoline and diesel engines, with and without inter-coolers, and with and without catalytic converters.
FIG. 1 is a simplified drawing of the prior art GM turbo-diesel turbocharger. Exhaust gas from the engine enters the turbine housing (106) through the port on the lower left (124) and puts pressure on the turbine wheel, causing it to spin. The exhaust gas, having passed through the turbine, exits through the exhaust port (110) to the remainder of the exhaust system, typically to a catalytic converter or directly to a tailpipe. The rotation of the turbine is transmitted to a compressor in a compressor housing (102) through a shaft in a shaft housing (104). The spinning compressor compresses air entering the compressor housing through the compressor inlet (100). The compressed air exits the turbocharger through the compressor outlet (130). The compressed air goes on to an inter-cooler or directly into the intake manifold of an engine.
The turbine housing (106) is fitted with a wastegate valve, not visible in FIG. 1. The valve is typically a poppet valve which, when opened, allows exhaust gas to pass directly into the turbine exhaust manifold (108) without having passed through the turbine wheel. The poppet valve moves by rotation about a wastegate shaft (112), such that if the valve changes from a closed to an open position, the wastegate shaft (112) rotates. This shaft exits the turbine housing (106). In FIG. 1, the arrow around the wastegate shaft (112) indicates the direction of rotation to open the valve, and the drawing shows the wastegate shaft (112) and its attached wastegate lever-arm (116) in the closed position.
The wastegate valve is held closed by a counter-clockwise torque applied to the wastegate shaft (112) through the lever arm (116). This torque is the result of the force applied to the lever arm (116) by the control arm (122). The force on the control arm (122), in turn, is applied by a spring (134) acting against a flange (136) on the control arm (122) and the end of the spring canister (132) closest to the lever arm (116). The spring (134) is typically loaded into canister (132) in a compressed state, so that there is some non-zero force required to pull control arm (122) any further out of the canister (132). This initial compression force is transmitted into a force seating the wastegate valve in the closed position.
If the flow of exhaust gas is great enough, the turbine inlet pressure will build-up to a level large enough to overcome this seating force, and blow the wastegate valve open with a clockwise rotation of the wastegate shaft (112). This allows some of the high pressure exhaust gas in the turbine inlet bypass the turbine and flow directly into the turbine exhaust manifold (108). The counter-clockwise torque applied to the shaft, therefore, determines the maximum turbine inlet pressure achievable. Above the maximum pressure, the force on the face of the wastegate will generate a clockwise torque on the wastegate shaft (112) so great as to overcome the preset counter-clockwise torque and open the wastegate valve.
FIG. 2A and FIG. 2B are orthogonal views of a prior art lever-arm (116), typical of the GM turbo-diesel. The lever arm (116) is welded (114) to the wastegate shaft (112). The lever arm has a second through-hole (118) which is used in the connection of the control arm to the lever-arm.
FIGS. 3A, 3B, 3C, and 3D are views of the prior art control arm. FIG. 3A shows the control arm (122) including an pin (120) attached to and part of the control arm designed to fit in the through hole of the lever-arm, FIG. 2 (118), such that the control arm and lever-arm are rotatably attached. The groove in pin (120) accommodates a C-clip, which secures the pin (120) to the lever arm (116). FIG. 3B is the same control arm rotated 90° so that the circular cross-section of the pin (120) is visible. FIG. 3C is a view in the same orientation as FIG. 3A showing the control arm (122) as installed in the spring canister (132), which is cut-away to show the spring (134) acting against one end of the spring canister and the flange (136) at the end of the control am (122). FIG. 3D is another view in the same orientation, now showing the spring canister (132) without the cut-away, as attached to the mounting bracket (128), which is in turn bolted to the compressor housing (102). Bracket (128) is typically welded to the spring canister (132).